Array antennas are known which have the characteristic of being nondispersive. In this context we may mention the so-called "candlestick" array antenna in which a first-stage supply channel branches into second-stage supply channels which in turn are branched until a final stage is reached where all the supply channels so obtained are connected to radiating elements acting as individual feeds. Such an antenna structure, which contains a number of Magic Tees or dividers, is complex and bulky as well as, in many instances, heavy and expensive.
Another previously proposed structure for nondispersive antennas contains a supply guide working, via directional couplers, into guides supplying the individual feeds, the assembly being such that the electrical lengths of the supply circuits for the individual feeds are all the same.
This antenna structure, although less bulky than the first-mentioned one, is still rather complicated from the point of view of mechanical construction, especially if the number of individual feeds is high (of the order of a hundred).
Other kinds of nondispersive attennas may also be mentioned, in particular active lenses and reflector arrays which are supplied through free space from a single primary feed. However, such antennas have the disadvantage that their longitudinal dimensions are equal to the focal length of the system, which is considerable. Moreover, there is a danger of the primary radiation spilling over the periphery of the array, which may produce undesirable diffuse radiation.